diff --git a/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanAndroid.cs b/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanAndroid.cs
index e7562198ac09ffa11a68044d7138ed709e47c4f2..8f36a7e1a95260eb5ccbb52da82a961ad840b602 100644
--- a/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanAndroid.cs
+++ b/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanAndroid.cs
@@ -35,11 +35,7 @@ internal ECDiffieHellmanAndroid(SafeEcKeyHandle ecKeyHandle)
                 KeySizeValue = _key.KeySize;
             }
 
-            public override KeySizes[] LegalKeySizes =>
-                new[] {
-                    new KeySizes(minSize: 256, maxSize: 384, skipSize: 128),
-                    new KeySizes(minSize: 521, maxSize: 521, skipSize: 0)
-                };
+            public override KeySizes[] LegalKeySizes => s_defaultKeySizes.CloneKeySizesArray();
 
             protected override void Dispose(bool disposing)
             {
diff --git a/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanCng.cs b/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanCng.cs
index b79dd9474a91dd23ede71da093ac6d5732e29bcf..a25cfcc3a4f6c769b8cab5a020a9f96268bedc85 100644
--- a/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanCng.cs
+++ b/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanCng.cs
@@ -66,17 +66,8 @@ private void ForceSetKeySize(int newKeySize)
             KeySizeValue = newKeySize;
         }
 
-        public override KeySizes[] LegalKeySizes
-        {
-            get
-            {
-                // Return the three sizes that can be explicitly set (for backwards compatibility)
-                return new[] {
-                    new KeySizes(minSize: 256, maxSize: 384, skipSize: 128),
-                    new KeySizes(minSize: 521, maxSize: 521, skipSize: 0),
-                };
-            }
-        }
+        // Return the three sizes that can be explicitly set (for backwards compatibility)
+        public override KeySizes[] LegalKeySizes => s_defaultKeySizes.CloneKeySizesArray();
 
         public override byte[] DeriveKeyFromHash(
             ECDiffieHellmanPublicKey otherPartyPublicKey,
diff --git a/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanOpenSsl.cs b/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanOpenSsl.cs
index 7855638b639ea32ba2c835d76cf400452c29c8d7..2f962e19fc3ef08fe560646d265d73263e3f5ade 100644
--- a/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanOpenSsl.cs
+++ b/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanOpenSsl.cs
@@ -45,11 +45,7 @@ public ECDiffieHellmanOpenSsl(int keySize)
             _key = new ECOpenSsl(this);
         }
 
-        public override KeySizes[] LegalKeySizes =>
-            new[] {
-                new KeySizes(minSize: 256, maxSize: 384, skipSize: 128),
-                new KeySizes(minSize: 521, maxSize: 521, skipSize: 0)
-            };
+        public override KeySizes[] LegalKeySizes => s_defaultKeySizes.CloneKeySizesArray();
 
         protected override void Dispose(bool disposing)
         {
diff --git a/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanSecurityTransforms.cs b/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanSecurityTransforms.cs
index dd5a73838a1592ddbe0405e9daafeb5913ae7cfb..496ee77897037213de932db0e1c27af6fa42bfea 100644
--- a/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanSecurityTransforms.cs
+++ b/src/libraries/Common/src/System/Security/Cryptography/ECDiffieHellmanSecurityTransforms.cs
@@ -27,18 +27,8 @@ internal ECDiffieHellmanSecurityTransforms(SafeSecKeyRefHandle publicKey, SafeSe
                 KeySizeValue = _ecc.SetKeyAndGetSize(SecKeyPair.PublicPrivatePair(publicKey, privateKey));
             }
 
-            public override KeySizes[] LegalKeySizes
-            {
-                get
-                {
-                    // Return the three sizes that can be explicitly set (for backwards compatibility)
-                    return new[]
-                    {
-                        new KeySizes(minSize: 256, maxSize: 384, skipSize: 128),
-                        new KeySizes(minSize: 521, maxSize: 521, skipSize: 0),
-                    };
-                }
-            }
+            // Return the three sizes that can be explicitly set (for backwards compatibility)
+            public override KeySizes[] LegalKeySizes => s_defaultKeySizes.CloneKeySizesArray();
 
             public override int KeySize
             {
diff --git a/src/libraries/Common/src/System/Security/Cryptography/ECDsaAndroid.cs b/src/libraries/Common/src/System/Security/Cryptography/ECDsaAndroid.cs
index 3b09a8045d029cc2392461830f0fe40f81fe9975..0aac5fc91d94414a89eb8d8170ea2cdb42a27fea 100644
--- a/src/libraries/Common/src/System/Security/Cryptography/ECDsaAndroid.cs
+++ b/src/libraries/Common/src/System/Security/Cryptography/ECDsaAndroid.cs
@@ -68,17 +68,8 @@ private void ForceSetKeySize(int newKeySize)
                 KeySizeValue = newKeySize;
             }
 
-            public override KeySizes[] LegalKeySizes
-            {
-                get
-                {
-                    // Return the three sizes that can be explicitly set (for backwards compatibility)
-                    return new[] {
-                        new KeySizes(minSize: 256, maxSize: 384, skipSize: 128),
-                        new KeySizes(minSize: 521, maxSize: 521, skipSize: 0),
-                    };
-                }
-            }
+            // Return the three sizes that can be explicitly set (for backwards compatibility)
+            public override KeySizes[] LegalKeySizes => s_defaultKeySizes.CloneKeySizesArray();
 
             public override byte[] SignHash(byte[] hash)
             {
diff --git a/src/libraries/Common/src/System/Security/Cryptography/ECDsaCng.cs b/src/libraries/Common/src/System/Security/Cryptography/ECDsaCng.cs
index 0edc06e488069958c402b17de9ff844e2d5731b1..426a6bdd4ad051862131480f0d3175722530fd8a 100644
--- a/src/libraries/Common/src/System/Security/Cryptography/ECDsaCng.cs
+++ b/src/libraries/Common/src/System/Security/Cryptography/ECDsaCng.cs
@@ -83,16 +83,7 @@ private void ForceSetKeySize(int newKeySize)
             KeySizeValue = newKeySize;
         }
 
-        public override KeySizes[] LegalKeySizes
-        {
-            get
-            {
-                // Return the three sizes that can be explicitly set (for backwards compatibility)
-                return new[] {
-                    new KeySizes(minSize: 256, maxSize: 384, skipSize: 128),
-                    new KeySizes(minSize: 521, maxSize: 521, skipSize: 0),
-                };
-            }
-        }
+        // Return the three sizes that can be explicitly set (for backwards compatibility)
+        public override KeySizes[] LegalKeySizes => s_defaultKeySizes.CloneKeySizesArray();
     }
 }
diff --git a/src/libraries/Common/src/System/Security/Cryptography/ECDsaOpenSsl.cs b/src/libraries/Common/src/System/Security/Cryptography/ECDsaOpenSsl.cs
index 0e681955ae5e36e4aca34301d602cbb01e859d16..242711f8e5cf43997ac7e2139fbfdef4b250c06e 100644
--- a/src/libraries/Common/src/System/Security/Cryptography/ECDsaOpenSsl.cs
+++ b/src/libraries/Common/src/System/Security/Cryptography/ECDsaOpenSsl.cs
@@ -78,17 +78,8 @@ private void ForceSetKeySize(int newKeySize)
             KeySizeValue = newKeySize;
         }
 
-        public override KeySizes[] LegalKeySizes
-        {
-            get
-            {
-                // Return the three sizes that can be explicitly set (for backwards compatibility)
-                return new[] {
-                    new KeySizes(minSize: 256, maxSize: 384, skipSize: 128),
-                    new KeySizes(minSize: 521, maxSize: 521, skipSize: 0),
-                };
-            }
-        }
+        // Return the three sizes that can be explicitly set (for backwards compatibility)
+        public override KeySizes[] LegalKeySizes => s_defaultKeySizes.CloneKeySizesArray();
 
         public override byte[] SignHash(byte[] hash)
         {
diff --git a/src/libraries/Common/src/System/Security/Cryptography/ECDsaSecurityTransforms.cs b/src/libraries/Common/src/System/Security/Cryptography/ECDsaSecurityTransforms.cs
index 7eaeb3b0b360db695da5281acb60dc544b2618d4..e02ea25ae2f0fd1fff680a474daf0e21730873f2 100644
--- a/src/libraries/Common/src/System/Security/Cryptography/ECDsaSecurityTransforms.cs
+++ b/src/libraries/Common/src/System/Security/Cryptography/ECDsaSecurityTransforms.cs
@@ -28,17 +28,8 @@ internal ECDsaSecurityTransforms(SafeSecKeyRefHandle publicKey, SafeSecKeyRefHan
                 KeySizeValue = _ecc.SetKeyAndGetSize(SecKeyPair.PublicPrivatePair(publicKey, privateKey));
             }
 
-            public override KeySizes[] LegalKeySizes
-            {
-                get
-                {
-                    // Return the three sizes that can be explicitly set (for backwards compatibility)
-                    return new[] {
-                        new KeySizes(minSize: 256, maxSize: 384, skipSize: 128),
-                        new KeySizes(minSize: 521, maxSize: 521, skipSize: 0),
-                    };
-                }
-            }
+            // Return the three sizes that can be explicitly set (for backwards compatibility)
+            public override KeySizes[] LegalKeySizes => s_defaultKeySizes.CloneKeySizesArray();
 
             public override int KeySize
             {
diff --git a/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/ECAlgorithm.cs b/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/ECAlgorithm.cs
index 8362bd705721d8c7cb1f9c3ccd41a589549ef396..5acdad43f82eaf021c13b20fb206fe2da01ff868 100644
--- a/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/ECAlgorithm.cs
+++ b/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/ECAlgorithm.cs
@@ -19,6 +19,12 @@ public abstract class ECAlgorithm : AsymmetricAlgorithm
             // ECDH and ECMQV are not valid in this context.
         };
 
+        private protected static readonly KeySizes[] s_defaultKeySizes =
+        {
+            new KeySizes(minSize: 256, maxSize: 384, skipSize: 128),
+            new KeySizes(minSize: 521, maxSize: 521, skipSize: 0),
+        };
+
         /// <summary>
         /// When overridden in a derived class, exports the named or explicit <see cref="ECParameters" /> for an ECCurve.
         /// If the curve has a name, the Curve property will contain named curve parameters otherwise it will contain explicit parameters.